Microstructure and relative humidity effects on long-term indentation creep properties of calcium carbonate cement
Jesus Rodriguez Sanchez, Physics
Cementitious materials are of key importance to the society. However, cement production contributes up to 5% of CO2 emissions, showing a clear need to develop more environmental-friendly approaches. Natural cements like limestone, with high carbonate content, have been widely used in construction, monuments and sculptures, but all these carbonate materials are prone to damage, e.g., by creep. In the present study, we have synthesized free-CO2 calcium carbonate cement as a proxy to investigate creep properties of pure carbonate materials and extract valuable information to build up strategies to avoid their degradation.
Calcium carbonate cements have been synthesized by mixing amorphous calcium carbonate (ACC) and vaterite (V) with water. The effect of microstructure is studied by preparing and testing samples with varied mixture design (ACC:V ratio) while the effect of moisture is studied by conditioning and testing those compositions in various relative humidity (RH) conditions. Creep experiments have been carried out over hardened samples with the long-term validated micro-indentation technique.
Results and conclusions
Regarding microstructure, creep results showed a clear trend: the larger the initial vaterite content of the paste, the lower the creep rate of the cement. Thus, larger vaterite derives on more elastic and resistant specimens due to the larger overall bridging area within the newly formed calcite crystals. Concerning relative humidity, a greater humidity led to a greater creep rate. The presence of water in pores enhances the local dissolution of calcite and makes the creep amplitude to rise.